session/logind: support CanGraphical property

backend/session/logind.c

@@ -35,7 +35,9 @@ struct logind_session {
 
 	char *id;
 	char *path;
+	char *seat_path;
 
+	bool can_graphical;
 	// specifies whether a drm device was taken
 	// if so, the session will be (de)activated with the drm fd,
 	// otherwise with the dbus PropertiesChanged on "active" signal
@@ -175,6 +177,34 @@ out:
 	return ret >= 0;
 }
 
+static bool find_seat_path(struct logind_session *session) {
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+			"/org/freedesktop/login1", "org.freedesktop.login1.Manager",
+			"GetSeat", &error, &msg, "s", session->base.seat);
+	if (ret < 0) {
+		wlr_log(WLR_ERROR, "Failed to get seat path: %s", error.message);
+		goto out;
+	}
+
+	const char *path;
+	ret = sd_bus_message_read(msg, "o", &path);
+	if (ret < 0) {
+		wlr_log(WLR_ERROR, "Could not parse seat path: %s", error.message);
+		goto out;
+	}
+	session->seat_path = strdup(path);
+
+out:
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+
+	return ret >= 0;
+}
+
 static bool session_activate(struct logind_session *session) {
 	int ret;
 	sd_bus_message *msg = NULL;
@@ -236,6 +266,7 @@ static void logind_session_destroy(struct wlr_session *base) {
 	sd_bus_unref(session->bus);
 	free(session->id);
 	free(session->path);
+	free(session->seat_path);
 	free(session);
 }
 
@@ -328,7 +359,7 @@ error:
 	return 0;
 }
 
-static int properties_changed(sd_bus_message *msg, void *userdata,
+static int session_properties_changed(sd_bus_message *msg, void *userdata,
 		sd_bus_error *ret_error) {
 	struct logind_session *session = userdata;
 	int ret = 0;
@@ -437,6 +468,95 @@ error:
 	return 0;
 }
 
+static int seat_properties_changed(sd_bus_message *msg, void *userdata,
+		sd_bus_error *ret_error) {
+	struct logind_session *session = userdata;
+	int ret = 0;
+
+	// if we have a drm fd we don't depend on this
+	if (session->has_drm) {
+		return 0;
+	}
+
+	// PropertiesChanged arg 1: interface
+	const char *interface;
+	ret = sd_bus_message_read_basic(msg, 's', &interface); // skip path
+	if (ret < 0) {
+		goto error;
+	}
+
+	if (strcmp(interface, "org.freedesktop.login1.Seat") != 0) {
+		// not interesting for us; ignore
+		wlr_log(WLR_DEBUG, "ignoring PropertiesChanged from %s", interface);
+		return 0;
+	}
+
+	// PropertiesChanged arg 2: changed properties with values
+	ret = sd_bus_message_enter_container(msg, 'a', "{sv}");
+	if (ret < 0) {
+		goto error;
+	}
+
+	const char *s;
+	while ((ret = sd_bus_message_enter_container(msg, 'e', "sv")) > 0) {
+		ret = sd_bus_message_read_basic(msg, 's', &s);
+		if (ret < 0) {
+			goto error;
+		}
+
+		if (strcmp(s, "CanGraphical") == 0) {
+			int ret;
+			ret = sd_bus_message_enter_container(msg, 'v', "b");
+			if (ret < 0) {
+				goto error;
+			}
+
+			ret = sd_bus_message_read_basic(msg, 'b', &session->can_graphical);
+			if (ret < 0) {
+				goto error;
+			}
+
+			return 0;
+		} else {
+			sd_bus_message_skip(msg, "{sv}");
+		}
+
+		ret = sd_bus_message_exit_container(msg);
+		if (ret < 0) {
+			goto error;
+		}
+	}
+
+	if (ret < 0) {
+		goto error;
+	}
+
+	ret = sd_bus_message_exit_container(msg);
+	if (ret < 0) {
+		goto error;
+	}
+
+	// PropertiesChanged arg 3: changed properties without values
+	sd_bus_message_enter_container(msg, 'a', "s");
+	while ((ret = sd_bus_message_read_basic(msg, 's', &s)) > 0) {
+		if (strcmp(s, "CanGraphical") == 0) {
+			session->can_graphical = sd_seat_can_graphical(session->base.seat);
+			return 0;
+		}
+	}
+
+	if (ret < 0) {
+		goto error;
+	}
+
+	return 0;
+
+error:
+	wlr_log(WLR_ERROR, "Failed to parse D-Bus PropertiesChanged: %s",
+		strerror(-ret));
+	return 0;
+}
+
 static bool add_signal_matches(struct logind_session *session) {
 	int ret;
 
@@ -471,7 +591,15 @@ static bool add_signal_matches(struct logind_session *session) {
 
 	ret = sd_bus_match_signal(session->bus, NULL, "org.freedesktop.login1",
 		session->path, "org.freedesktop.DBus.Properties", "PropertiesChanged",
-		properties_changed, session);
+		session_properties_changed, session);
+	if (ret < 0) {
+		wlr_log(WLR_ERROR, "Failed to add D-Bus match: %s", strerror(-ret));
+		return false;
+	}
+
+	ret = sd_bus_match_signal(session->bus, NULL, "org.freedesktop.login1",
+			session->seat_path, "org.freedesktop.DBus.Properties",
+			"PropertiesChanged", seat_properties_changed, session);
 	if (ret < 0) {
 		wlr_log(WLR_ERROR, "Failed to add D-Bus match: %s", strerror(-ret));
 		return false;
@@ -656,6 +784,12 @@ static struct wlr_session *logind_session_create(struct wl_display *disp) {
 		goto error;
 	}
 
+	if (!find_seat_path(session)) {
+		sd_bus_unref(session->bus);
+		free(session->path);
+		goto error;
+	}
+
 	if (!add_signal_matches(session)) {
 		goto error_bus;
 	}
@@ -672,6 +806,21 @@ static struct wlr_session *logind_session_create(struct wl_display *disp) {
 		goto error_bus;
 	}
 
+	// Check for CanGraphical first
+	session->can_graphical = sd_seat_can_graphical(session->base.seat);
+	if (!session->can_graphical) {
+		wlr_log(WLR_INFO, "Waiting for 'CanGraphical' on seat %s", session->base.seat);
+	}
+
+	while (!session->can_graphical) {
+		ret = wl_event_loop_dispatch(event_loop, -1);
+		if (ret < 0) {
+			wlr_log(WLR_ERROR, "Polling error waiting for 'CanGraphical' on seat %s",
+				session->base.seat);
+			goto error_bus;
+		}
+	}
+
 	wlr_log(WLR_INFO, "Successfully loaded logind session");
 
 	session->base.impl = &session_logind;
@@ -680,6 +829,7 @@ static struct wlr_session *logind_session_create(struct wl_display *disp) {
 error_bus:
 	sd_bus_unref(session->bus);
 	free(session->path);
+	free(session->seat_path);
 
 error:
 	free(session->id);